In known vehicle speed control systems, typically referred to as cruise control systems, a set-speed for the vehicle may be initially set by a user (e.g., driver). Once set by the user, the vehicle speed is maintained, on-rod without further intervention by the user so as to improve the driving experience for the user by reducing workload. So long as the speed control system remains in an active state, the speed control system attempts to maintain the speed of the vehicle at the designated set-speed as the vehicle progresses.
Use of a speed control system at low speeds when driving off-road may offer a user considerable advantage in reduced user workload and enhanced vehicle composure. However, if a user attempts to use a speed control system off-road, a powertrain controller, in an attempt to provide a sufficient amount of torque to overcome a high drag obstacle, may cause the amount of torque delivered to one or more wheels to overshoot an amount required to maintain the prevailing set speed and maintain vehicle composure when the level of drag reduces. This may cause an occupant of the vehicle to experience a variation in speed which may give rise to the vehicle body being perceived by the occupant as lurching.
In addition, known cruise control systems are intended primarily for off-road use, and so are arranged cancel in the event that a wheel slip event is detected requiring intervention by a traction control system (TCS) or stability control system (SCS). Accordingly, they are not well suited to maintaining vehicle progress when driving in off-road conditions or on slippery roads, where such events may be relatively common.
Accordingly, there is a need for a speed control system and method for use with the same that minimizes and/or eliminates one or mom of the above-identified deficiencies.